A Google data center outside Atlanta, Georgia, has partnered with the local municipality to use 100% waste water in an innovative approach to cooling.

The data center – built in 2007 – originally used potable water for evaporative cooling, a process that is roughly 50% more efficient than standard mechanical chillers. But Google says it realized it did not need water treated to drinking standards for its cooling purposes.

So the search-engine giant financed the building of a “sidestream” treatment plant that intercepts 30 percent of the recycled or grey water that would otherwise be released by the Douglas County Water and Sewer Authority (WSA) back into the region’s main waterway – the Chattahoochee River.

The sidestream plant cleans the water enough for the cooling process, and any remaining water that does not evaporate is sent to a second, effluent plant on the Google property before being returned to the Chattahoochee. The additional sterilization, filtration and chlorination processes actually make this water cleaner than the water released by WSA.

Peter Frost, the Executive Director of WSA says the arrangement is a “win-win.” A typical data center can use hundreds of thousands of gallons of water a day in evaporative cooling. By using waste water, Google doesn’t strain the municipality’s drinking water reservoir – a serious concern in the state, which has seen explosive growth and water demand in past decades while suffering increasingly severe droughts.

The arrangement benefits Google and Douglas County citizens, however it should be noted that evaporation towers like Google’s and others along the Chattahoochee significantly affect flow levels and the communities and ecosystems downstream that rely on the water.